code: def _load_oauth_credentials(self) -> Credentials:
      json_str = os.environ.get(self.gcs_credential_name)
      if not json_str:
          return None
  
      if os.path.isfile(json_str):
          return Credentials.from_service_account_file(json_str)
  
      return Credentials.from_service_account_info(json.loads(json_str))
  
file_path: gokart/gokart/gcs_config.py
imports: import json
  import os
  import luigi
  import luigi.contrib.gcs
  from google.oauth2.service_account import Credentials
label_desc: Use image node_id 3 for calling the GCSConfig obj's underlying member method code with example usage: obj._load_oauth_credentials() and returns: Credentials, None, Credentials